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CSEDI: Geochemical Evolution of the Earth's Mantle Constrained by Observations and Dynamical Modeling

CSEDI：观测和动力学模型约束下的地幔地球化学演化

基本信息

批准号：
1664642
负责人：
Peter van Keken
金额：
$ 29.38万
依托单位：
Carnegie Institution of Washington
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-08-01 至 2021-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1664642&HistoricalAwards=false
关键词：
CSEDI Geochemical Evolution Earth Mantle

项目摘要

This project seeks to advance scientific knowledge about how the Earth's interior has changed over geologic time, due to the very slow motions caused by the sinking of tectonic plates into the interior and the rise of hot buoyant material from the deep Earth, all of which work to mix the Earth's mantle. These convective motions have the potential to move tectonic plates from the surface all the way to the core-mantle boundary (CMB), and to return material from the CMB where it can contribute to near-surface melting that produces volcanoes at mid-ocean ridges and at oceanic hotspots (such as Hawaii and others). The investigators will use high-performance computer simulations of these convective motions to study the flow of the Earth's interior and how this flow is modified by changes in mineralogy that occur at the high pressures of the Earth's deep interior; the computational models will be enhanced by the inclusion of millions of passive tracer particles that record changes in geochemistry that occur when the mantle melts at the surface, when plates sink and mix into the Earth's interior, and when sediment eroded from the continents is brought into the Earth's interior by these processes. The geochemical changes recorded by the tracer particles will be compared with geochemical data from volcanoes to test whether the flow in the deep Earth continues all the way to the core, or whether the interior flows as separate layers with minimal mixing between them. The knowledge gained from this project will provide information on how the tectonic motions at the surface of the Earth affect mixing in the interior, and how this mixing in turn has altered the flow of various elements from the interior to the continents thus providing information on how the continents have grown and eroded over Earth's geologic history.In this project the investigators will focus on documenting the geochemical evolution of the mantle in a series of high-resolution numerical convection models that examine the degree of mantle layering, stratification, and convective isolation that occur when realistic compressible equations of state are used to describe the physical properties of the mantle. The use of a compressible mantle will allow us to model mineralogical phase transitions in a rigorous way. When combined with laboratory data on the P-T-strain rate dependence of mantle viscosity, conductivity and thermal expansion, these features of the model will produce the most physically realistic description of the extent of mantle layering that can occur due to depth-dependent density and viscosity associated with known phase boundaries. The model series will be further constrained to only those models that match the known ranges in major geophysical and geochemical observations (convective vigor, mantle temperature, heat flow, plate velocities, rate of internal heating, composition and mass of the atmosphere and continental crust, etc.). The geochemistry of the model space will be calculated from millions of active numerical tracers embedded in the mantle flow, that will each record the trace element fractionation and associated isotopic evolution they experience when their evolution is punctuated by melting, degassing, and continental extraction events that occur at the surface of the model. The team will model explicitly the evolving isotope geochemistry of both lithophile and noble gas isotope systems in the convecting mantle, continental crust and atmosphere, and quantitatively compare the model output with geochemical data to test the viability of our models.

该项目旨在增进关于地球内部在地质时期如何变化的科学知识，这是由于构造板块下沉到内部和地球深部热浮力物质上升造成的非常缓慢的运动，所有这些都有助于混合地球地幔。这些对流运动有可能将构造板块从地表一直移动到核幔边界（CMB），并将CMB的物质返回，从而有助于近地表熔融，从而在洋中脊和海洋热点（如夏威夷等）产生火山。调查人员将利用高性能计算机模拟这些对流运动，研究地球内部的流动，以及这种流动如何因地球深部高压下矿物学的变化而改变;计算模型将通过包含数百万个被动示踪粒子来增强，这些粒子记录了地幔在表面熔化时发生的地球化学变化，当板块下沉并混合到地球内部时，当大陆侵蚀的沉积物通过这些过程被带到地球内部时。示踪粒子记录的地球化学变化将与火山的地球化学数据进行比较，以测试地球深处的流动是否一直持续到地核，或者内部流动是否作为单独的层，它们之间的混合最小。从这个项目中获得的知识将提供关于地球表面的构造运动如何影响内部混合的信息，以及这种混合如何反过来改变了各种元素从内部流向大陆的流动，从而提供了关于大陆在地球地质历史上如何生长和侵蚀的信息。在这个项目中，研究人员将专注于记录地球的地球化学演化。地幔在一系列高分辨率数值对流模型，检查地幔分层，分层和对流隔离的程度时，发生现实的可压缩状态方程用于描述地幔的物理特性。可压缩地幔的使用将使我们能够以严格的方式模拟矿物学相变。当结合实验室数据的P-T-应变速率依赖地幔粘度，电导率和热膨胀，这些功能的模型将产生最真实的描述的程度地幔分层，可能会发生由于深度依赖的密度和粘度与已知的相边界。模型系列将进一步限于与主要地球物理和地球化学观测的已知范围相匹配的那些模型（对流活力、地幔温度、热流、板块速度、内部加热速率、大气和大陆地壳的组成和质量等）。模型空间的地球化学将从嵌入地幔流中的数百万个活跃的数值示踪剂中计算出来，每个示踪剂都将记录微量元素分馏和相关的同位素演化，当它们的演化被发生在模型表面的熔融、脱气和大陆提取事件打断时，它们经历了这些演化。该团队将明确模拟对流地幔，大陆地壳和大气中亲石和惰性气体同位素系统的同位素地球化学演变，并将模型输出与地球化学数据进行定量比较，以测试我们模型的可行性。

项目成果

期刊论文数量（6）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Subducted oceanic crust as the origin of seismically slow lower-mantle structures

DOI：
10.1186/s40645-020-00327-1
发表时间：
2020-05-21
期刊：
PROGRESS IN EARTH AND PLANETARY SCIENCE
影响因子：
3.9
作者：
Jones, Timothy D.;Maguire, Ross R.;Koelemeijer, Paula
通讯作者：
Koelemeijer, Paula

A Role for Subducted Oceanic Crust in Generating the Depleted Mid‐Ocean Ridge Basalt Mantle

俯冲洋壳在生成耗尽的洋中脊玄武岩地幔中的作用

DOI：
10.1029/2020gc009148
发表时间：
2020
期刊：
Geosystems
影响因子：
0
作者：
Tucker, Jonathan M.;van Keken, Peter E.;Jones, Rosemary E.;Ballentine, Chris J.
通讯作者：
Ballentine, Chris J.

Origins of the terrestrial Hf-Nd mantle array: Evidence from a combined geodynamical-geochemical approach

DOI：
10.1016/j.epsl.2019.04.015
发表时间：
2019-07
期刊：
Earth and Planetary Science Letters
影响因子：
5.3
作者：
Rosemary E. Jones;P. V. van Keken;E. Hauri;J. Tucker;J. Vervoort;C. Ballentine
通讯作者：
Rosemary E. Jones;P. V. van Keken;E. Hauri;J. Tucker;J. Vervoort;C. Ballentine

An Exactly Mass Conserving and Pointwise Divergence Free Velocity Method: Application to Compositional Buoyancy Driven Flow Problems in Geodynamics

精确质量守恒和逐点发散自由速度方法：在地球动力学中组合浮力驱动流问题中的应用